v., n., & adj.
v. 1 intr. & tr. (foll. by in, out, past, away, etc.) go or convey furtively; slink. 2 tr. sl. steal unobserved; make off with. 3 intr. Brit. schoolsl. tell tales; turn informer. 4 intr. (as sneaking adj.) a furtive; undisclosed (have a sneaking affection for him). b persistent in one's mind; nagging (a sneaking feeling that it is not right).
n. 1 a mean-spirited cowardly underhand person. 2 Brit. schoolsl. a tell-tale.
adj. acting or done without warning; secret (a sneak attack). sneak-thief a thief who steals without breaking in; a pickpocket. sneakingly adv.
[ 16th c., prob. dial.: perh. rel. to ME snike, OE snican creep ]